Shigenori Fujine

Diffusion coefficient measurement of lithium ion in sintered Li1.33Ti1.67O4 by means of neutron radiography

Neutron radiography (NR) using cold neutron beam was applied to the tracer diffusion coefficient measurement of lithium ion in Li1.33Ti1.67O4. The diffusion couples with different lithium isotope concentrations were annealed at 860 to 900°C and the isotope profiles of lithium ion in the sample were measured by NR. The diffusion profiles obtained for the samples annealed at higher temperatures show good agreement with Fick’s law, whereas the diffusion was not carried out well at the interface for the lower-temperature-annealed samples. The values of diffusion coefficients obtained from the profile fitting were a little smaller than those expected from the electric conductivity. The NR method was found to be the most useful method to measure the tracer diffusion coefficient of lithium ion in solids.

Visualization of fluid phenomena using a high frame-rate neutron radiography with a steady thermal neutron beam

Abstract Experiments on visualization of fluid phenomena in a metallic vessel were conducted using a high-speed video camera with a steady thermal neutron beam. The Japan Research Reactor 3M, whose flux at the imaging plate is 1.5 × 10 8 n/cm 2 s, of Japan Atomic Energy Research Institute was used as a neutron source. The imaging system for high frame-rate neutron radiography with the steady thermal neutron beam consisted of a high sensitivity scintillator, 6 LiF/ZnS:Ag, an image intensifier whose gain was a factor of 100 000 at the maximum, and a high-speed video which could record phenomena at 1000 frames/s for 14 min by using an ordinary VHS tape with the recording time of 120 min at the normal speed. Visualization of air-water two-phase flows in a rectangular duct with 2.4 mm gap and 40 mm width were successfully performed with the steady thermal neutron beam and this imaging system at frame rates up to 1000 frames/s. The shapes and the behavior of bubbles and liquid films were clearly observed. The rising velocities of slug bubbles and the flow regimes could be also measured. It was clarified that this new technique may have significant advantages both in visualizing and measuring high-speed phenomena when the visible light is not applicable.

Development of imaging techniques for fast neutron radiography in Japan

Abstract Neutron radiography with fast neutron beams (FNR) has been studied at the fast neutron source reactor “YAYOI” of the University of Tokyo since 1986. Imaging techniques for FNR have been developed for CR-39 track-etch detector, electronic imaging system (television method), direct film method, imaging plate and also fast and thermal neutron concurrent imaging method. The review of FNR imaging techniques and some applications are reported in this paper.

Lithium batteries: Application of neutron radiography

Abstract Several kinds of primary and secondary commercial lithium batteries, such as CR1/3 · 1H (Fujitsu), CR1220 and BR435 (Panasonic), ML1220 (Sanyo Excel) were investigated using neutron radiography; the variation of the lithium distribution inside these batteries upon discharging (and charging) were clarified by analyzing their visualized images. It was demonstrated that neutron radiography is a potential and useful method, especially in evaluating the reversibility of rechargeable batteries, which have been used under different discharging/charging conditions.

Visualization of hydrogen in hydrogen storage alloys using neutron radiography

Abstract Small amounts of hydrogen in hydrogen storage alloys, such as Mg2Ni, were detected using neutron radiography (NRG). Hydrogen concentrations in a hydrogenated solid solution were determined by this technique. Furthermore, we were able to obtain NRG images for an initial stage of hydrogen absorption in the hydrogen storage alloys. NRG would be a new method of measurement to clarify the behavior of hydrogen in hydrogen storage alloys.

Analysis of hydrogen distribution in hydrogen storage alloy using neutron radiography

Abstract The initial stage of hydrogen absorption was investigated on Mg–Ni based alloys, such as Mg2Ni and Mg3Ni (the eutectic mixture of Mg2Ni and Mg), using neutron radiography (NRG). The NRG images were obtained by not only a simple transmission method but also a tomographic one, which could clearly visualize hydrogen distribution in the alloys. The hydrogen diffusion coefficient in these alloys was estimated to be ≈2×10−7 cm2 s−1 from the change in hydrogen absorption depth with hydrogenation time. The comparison of the volume expansion rate due to hydrogen absorption for the alloys showed that Mg3Ni has better toughness than Mg2Ni until Mg3Ni was partly degraded to form magnesium hydride. Thus, NRG was found to be a powerful tool to clarify the behavior of hydrogen in hydrogen storage alloys.

Application of Neutron Radiography to Visualize the Motion of Lithium Ions in Lithium‐Ion Conducting Materials

Neutron radiography (NR) has been applied to a lithium in conducting spinel-type oxide Li{sub 1.33}Ti{sub 1.67}O{sub 4} in order to visualize the movement of lithium ions. After dc current was passed for electrolysis through specially prepared oxides with different isotope ratios ({sup 6}Li/{sup 7}Li), a set of NR images was obtained that illustrate the lithium ion conduction in the oxide. Analysis of the NR images determined that the transport number of lithium ions in the spinel-type Li{sub 1.33}Ti{sub 1.67}O{sub 4} is 0.99 at 900 C, which is almost the same as that measured by the oxygen concentration cell method. Further detailed analysis was carried out to investigate which kind of lithium ion in the oxide ion array of the spinel-type structure contributes to the electric conduction, the tetrahedral A site lithium, the octahedral B site, or both of these. As a result, the contribution of A site lithium to ionic conduction was confirmed.

Studies on the lithium ion conduction in Ca0.95Li0.10WO4 using cold neutron radiography

Abstract Cold neutron radiography (CNR) was applied to study the lithium ion conduction in the substituted scheelite-type oxide of Ca 0.95 Li 0.10 WO 4 . The lithium ion distribution profiles were obtained from a set of neutron radiography (NR) images of the electrolyzed oxides having different 6 Li/ 7 ratios. They showed that the lithium ion transport number of the oxide is 0.99, which coincided with the value derived from the EMF measurement of an oxygen gas concentration cell. Furthermore, they denoted that the lithium ion conduction was preferably ascribed to lithium ions in the interstitial sites.

An on-line video image processing system for real-time neutron radiography

Abstract The neutron radiography system installed at the E-2 experimental hole of the KUR (Kyoto University Reactor) has been used for some NDT applications in the nuclear field. The on-line video image processing system of this facility is introduced in this paper. A 0.5 mm resolution in images was obtained by using a super high quality TV camera developed for X-radiography viewing a NE-426 neutron-sensitive scintillator. The image of the Ne-426 on a CRT can be observed directly and visually, thus many test samples can be sequentially observed when necessary for industrial purposes. The video image signals from the TV camera are digitized, with a 33 ms delay, through a video A/D converter (ADC) and can be stored in the image bufer (32KB DRAM) of a microcomputer (Z-80) system. The digitized pictures are taken with 16 levels of gray scale and resolved to 240×256 picture elements (pixels) on a monochrome CRT, with the capability also to display 16 distinct colors on a RGB video display. The direct image of this system could be satisfactory for penetrating the side plates to test MTR type reactor fuels and for the investigation of moving objects.

Visualization and correlation analysis of counter-current two-phase flow in a thermosyphon by neutron radiography

Abstract We visualized the working fluid behavior in a bent thermosyphon by a neutron radiography and analyzed it quantitatively with an image processing technique. Working fluid velocity was evaluated by the two-point correlation function and also the spatio-temporal correlation was calculated, which led to a clarification of the pass route of working fluid in the thermosyphon. The probability density function of the void fraction was calculated.